Two string - C++ cin vs gets, scanf, while loop, pointer - calculation

Twostring9.cpp

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>

#define INF (1<<30)
#define mod 666013

using namespace std;
int n, i, T, o, m, f[35];
char b[100005], a[100005];
int main()
{
    //freopen("1.in", "r", stdin);
    //freopen("1.out", "w", stdout);
    scanf("%d\n", &T);
    while(T--)
    {
        for(i=0;i<=30;i++)
            f[i]=0;
        gets(a+1);
        gets(b+1);
        n=strlen(a+1);
        m=strlen(b+1);
        for(i=1;i<=n;i++)
            f[a[i]-'a']=1;
        o=0;
        for(i=1;i<=m;i++)
            if(f[b[i]-'a']==1)
            {
                printf("YES\n");
                o=1;
                break;
            }
        if(o==0)
            printf("NO\n");
    }
    return 0;
}